The present invention relates to a CATV terminal unit for selecting chargeable programs to be watched and for providing selected programs to a viewer.
In a conventional CATV terminal unit of this kind, there is provided an "Impulse pay per view (IPPV)" function in which a charge for the pay per view (PPV) program to be watched is paid just before the program is received. With an IPPV function when a channel is designated and selected by a ten-key pad for transmitting the pay per view program, the terminal unit selects a chargeable announcing channel without directly selecting the designated channel. In this state, when the TV viewer presses an authorizing key, the terminal unit selects the pay TV channel on which the program is transmitted and provides the viewer with the desired program. (The terms chargeable and pay per view are used interchangeably throughout.)
FIG. 1 is a block diagram of a conventional CATV terminal unit of the type described above. A terminal unit 11 is connected to the CATV head end via an input terminal IN and a transmission line such as a coaxial cable, etc. An RF signal composed of a video signal, etc., is transmitted from the head end through the transmission line. The transmission line is also utilized to perform a mutual communication of various kinds of data between the head end and CATV terminal unit 11.
The RF signal transmitted from the head end is distributed by a distributor 111 and is applied to a converter 112 and data-receiving section 113. The converter 112 selects a specific channel based on a selecting signal from a controller 114 composed of a CPU, and frequency-converts the signal of the selected channel to a frequency corresponding to a reserved channel, e.g., channel 3. The frequency-converted signal of the specific channel is inputted to a descrambler 115 and is descrambled by the descrambler 115, assuming descrambling is necessary, and passes through the descrambler 115 without descrambling when this signal has not been scrambled. The signal passed through the descrambler 115 is applied to a TV receiver 13 from an output terminal OUT.
The signal applied to the descrambler 115 through the converter 112 comprises in-band data including scramble data superimposed on an audio signal. The in-band data are extracted by the descrambler 115 and applied to the controller 114. The controller 114 controls the operation of the descrambler 115 so as to descramble the video signal based on the descramble data in the in-band data applied from the descrambler 115.
The data-receiving section 113 extracts various kinds of data transmitted by the specific channel in the RF signal distributed by the distributor 111 and applies the extracted data to the controller 114.
The controller 114 is connected to a keyboard 116 used for selecting the channel, etc., and the above selecting signal is generated by the key operation of the keyboard 116. The keyboard 116 has a key or keys for channel selection and a number of other keys such as a key for turning the power on and off, an authorizing key for confirming the pay per view program before actual viewing a key for adjusting the sound volume, etc. Signals generated by the operations of such keys are applied to the controller 114.
The controller 114 is further connected to a display section 117 and remote control signal-receiving section 118. In the display section 117, various kinds of operating states, messages, etc., are displayed under the control of the controller 114. A remote control optical signal emitted from an unillustrated remote control device is received by the remote control signal-receiving section 118, and is converted into an electric signal and applied to the controller 114. The remote control device can generate most or all the signals generated by the keyboard 116.
Whether or not a program of the channel selected by the viewer is a chargeable or pay per view program is determined by event code data included in the in-band data of the selected channel. However, the event code may be changed by a noise, etc., so as to indicate that the program is a pay program when it is a free program. If this occurs, the CATV terminal selects a chargeable announcing channel. Once such a state occurs, the system does not return to the original channel by pressing the authorizing key unless the viewer selects the channel again, which operation is cumbersome to the viewer.
Further, since this system requires one channel to be reserved for announcing that a selected program is a pay per view channel, the number of channels available for programming is reduced by one.